EvtSSDCP.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 2001      Caltech
//
// Module: EvtSSDCP.cc
//
// Description: See EvtSSDCP.hh
//
// Modification history:
//
//    RYD       August 12, 2001        Module created
//    F. Sandrelli, Fernando M-V  March 1, 2002     Debugged and added z parameter (CPT violation)
//------------------------------------------------------------------------
// 
#include "EvtGenBase/EvtPatches.hh"
#include <stdlib.h>
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtRandom.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtCPUtil.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtVector4C.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenModels/EvtSSDCP.hh"
#include <string>
#include "EvtGenBase/EvtConst.hh"
using std::endl;
 
EvtSSDCP::~EvtSSDCP() {}
 
void EvtSSDCP::getName(std::string& model_name){
 
  model_name="SSD_CP";     
 
}
 
 
EvtDecayBase* EvtSSDCP::clone(){
 
  return new EvtSSDCP;
 
}
 
void EvtSSDCP::init(){
 
  // check that there are 8 or 12 or 14 arguments
 
  checkNArg(14,12,8);
  checkNDaug(2);
 
  EvtSpinType::spintype d1type=EvtPDL::getSpinType(getDaug(0));
  EvtSpinType::spintype d2type=EvtPDL::getSpinType(getDaug(1));
 
  // FS commented this check to include alias of B0
  //  if ( !((getParentId() == EvtPDL::getId("B0"))||(getParentId() == EvtPDL::getId("B0B"))) ) {
  //    report(ERROR, "EvtGen") << "EvtSSDCP cannot decay "
  //            << EvtPDL::name(getParentId()) 
  //            << ". Must be specified to decay"
  //            << " only B0 or a B0B ." << endl;
  //  report(ERROR,"EvtGen") << "Will terminate execution!"<<endl;
  //  ::abort();
  //}
 
  if ( (!(d1type == EvtSpinType::SCALAR || d2type == EvtSpinType::SCALAR))||
       (!((d2type==EvtSpinType::SCALAR)||(d2type==EvtSpinType::VECTOR)||(d2type==EvtSpinType::TENSOR)))||
       (!((d1type==EvtSpinType::SCALAR)||(d1type==EvtSpinType::VECTOR)||(d1type==EvtSpinType::TENSOR)))
       ) {
    report(ERROR,"EvtGen") << "EvtSSDCP generator expected "
                           << "one of the daugters to be a scalar, the other either scalar, vector, or tensor, found:"
               << EvtPDL::name(getDaug(0)).c_str()<<" and "<<EvtPDL::name(getDaug(1)).c_str()<<endl;
    report(ERROR,"EvtGen") << "Will terminate execution!"<<endl;
    ::abort();
  }
 
  _dm=getArg(0)/EvtConst::c; //units of 1/mm
 
  _dgog=getArg(1);
 
  
  _qoverp=getArg(2)*EvtComplex(cos(getArg(3)),sin(getArg(3)));
  _poverq=1.0/_qoverp;
 
  _A_f=getArg(4)*EvtComplex(cos(getArg(5)),sin(getArg(5)));
 
  _Abar_f=getArg(6)*EvtComplex(cos(getArg(7)),sin(getArg(7)));
  
  if (getNArg()>=12){
    _eigenstate=false;
    _A_fbar=getArg(8)*EvtComplex(cos(getArg(9)),sin(getArg(9)));
    _Abar_fbar=getArg(10)*EvtComplex(cos(getArg(11)),sin(getArg(11)));
  }
  else{
    //I'm somewhat confused about this. For a CP eigenstate set the
    //amplitudes to the same. For a non CP eigenstate CPT invariance
    //is enforced. (ryd)
    if (
    (getDaug(0)==EvtPDL::chargeConj(getDaug(0))&&
     getDaug(1)==EvtPDL::chargeConj(getDaug(1)))||
    (getDaug(0)==EvtPDL::chargeConj(getDaug(1))&&
     getDaug(1)==EvtPDL::chargeConj(getDaug(0)))){
      _eigenstate=true;
    }else{
      _eigenstate=false;
      _A_fbar=conj(_Abar_f);
      _Abar_fbar=conj(_A_f);
    }
  }
 
  //FS: new check for z 
  if (getNArg()==14){ //FS Set _z parameter if provided else set it 0
    _z=EvtComplex(getArg(12),getArg(13));
  }
  else{
    _z=EvtComplex(0.0,0.0);
  }
 
  // FS substituted next 2 lines...
 
 
  //
  //  _gamma=EvtPDL::getctau(EvtPDL::getId("B0"));  //units of 1/mm
  //_dgamma=_gamma*0.5*_dgog;
  //
  // ...with:
 
  _gamma=1/EvtPDL::getctau(EvtPDL::getId("B0")); //gamma/c (1/mm)
  _dgamma=_gamma*_dgog;  //dgamma/c (1/mm) 
 
  if (verbose()){
    report(INFO,"EvtGen") << "SSD_CP will generate CP/CPT violation:"
              << endl << endl
              << "    " << EvtPDL::name(getParentId()).c_str() << " --> "
              << EvtPDL::name(getDaug(0)).c_str() << " + "
              << EvtPDL::name(getDaug(1)).c_str() << endl << endl
              << "using parameters:" << endl << endl
              << "  delta(m)  = " << _dm << " hbar/ps" << endl
              << "dGamma      = "  << _dgamma <<" ps-1" <<endl
              << "       q/p  = " << _qoverp << endl  
              << "        z  = " << _z << endl  
              << "       tau  = " << 1./_gamma << " ps" << endl;
  }
 
}
 
void EvtSSDCP::initProbMax() {
  double theProbMax = 
    abs(_A_f) * abs(_A_f) +
    abs(_Abar_f) * abs(_Abar_f) +
    abs(_A_fbar) * abs(_A_fbar) +
    abs(_Abar_fbar) * abs(_Abar_fbar);
 
  if (_eigenstate) theProbMax*=2;
 
  EvtSpinType::spintype d2type=EvtPDL::getSpinType(getDaug(1));
  EvtSpinType::spintype d1type=EvtPDL::getSpinType(getDaug(0));
  if (d1type==EvtSpinType::TENSOR||d2type==EvtSpinType::TENSOR) theProbMax*=10;
 
  setProbMax(theProbMax);
}
 
void EvtSSDCP::decay( EvtParticle *p){
 
  static EvtId B0=EvtPDL::getId("B0");
  static EvtId B0B=EvtPDL::getId("anti-B0");
  
  double t;
  EvtId other_b;
  EvtId daugs[2];
 
  int flip=0;
  if (!_eigenstate){
    if (EvtRandom::Flat(0.0,1.0)<0.5) flip=1;
  }
 
  if (!flip) {
    daugs[0]=getDaug(0);
    daugs[1]=getDaug(1);
  }
  else{
    daugs[0]=EvtPDL::chargeConj(getDaug(0));
    daugs[1]=EvtPDL::chargeConj(getDaug(1));
  }
 
  EvtParticle *d;
  p->initializePhaseSpace(2, daugs);
 
  EvtComplex amp;
 
 
  EvtCPUtil::OtherB(p,t,other_b,0.5); // t is c*Dt (mm)
 
  //if (flip) t=-t;
 
  //FS We assume DGamma=GammaLow-GammaHeavy and Dm=mHeavy-mLow
  EvtComplex expL=exp(-EvtComplex(-0.25*_dgamma*t,0.5*_dm*t));
  EvtComplex expH=exp(EvtComplex(-0.25*_dgamma*t,0.5*_dm*t));
  //FS Definition of gp and gm
  EvtComplex gp=0.5*(expL+expH);
  EvtComplex gm=0.5*(expL-expH);
  //FS Calculation os sqrt(1-z^2) 
  EvtComplex sqz=sqrt(abs(1-_z*_z))*exp(EvtComplex(0,arg(1-_z*_z)/2));
  
  //EvtComplex BB=0.5*(expL+expH);                  // <B0|B0(t)>
  //EvtComplex barBB=_qoverp*0.5*(expL-expH);       // <B0bar|B0(t)>
  //EvtComplex BbarB=_poverq*0.5*(expL-expH);       // <B0|B0bar(t)>
  //EvtComplex barBbarB=BB;                         // <B0bar|B0bar(t)>
  //  FS redefinition of these guys... (See BAD #188 eq.35 for ref.)
  //  q/p is taken as in the BaBar Phys. Book (opposite sign wrt ref.)
  EvtComplex BB=gp+_z*gm;                 // <B0|B0(t)>
  EvtComplex barBB=sqz*_qoverp*gm;       // <B0bar|B0(t)>
  EvtComplex BbarB=sqz*_poverq*gm;       // <B0|B0bar(t)>
  EvtComplex barBbarB=gp-_z*gm;           // <B0bar|B0bar(t)>
 
  if (!flip){
    if (other_b==B0B){
      //at t=0 we have a B0
      //report(INFO,"EvtGen") << "B0B"<<endl;
      amp=BB*_A_f+BbarB*_Abar_f;
      //std::cout << "noflip B0B tag:"<<amp<<std::endl;
      //amp=0.0;
    }
    if (other_b==B0){
      //report(INFO,"EvtGen") << "B0"<<endl;
      amp=barBB*_A_f+barBbarB*_Abar_f;
    }
  }else{
    if (other_b==B0){
      amp=barBB*_A_fbar+barBbarB*_Abar_fbar;
      //std::cout << "flip B0 tag:"<<amp<<std::endl;
      //amp=0.0;
    }
    if (other_b==B0B){
      amp=BB*_A_fbar+BbarB*_Abar_fbar;
    }
  }
 
 
  EvtVector4R p4_parent=p->getP4Restframe();
  double m_parent=p4_parent.mass();
 
  EvtSpinType::spintype d2type=EvtPDL::getSpinType(getDaug(1));
 
  EvtVector4R momv;
  EvtVector4R moms;
 
  if (d2type==EvtSpinType::SCALAR){
    d2type=EvtPDL::getSpinType(getDaug(0));
    d= p->getDaug(0);
    momv = d->getP4();
    moms = p->getDaug(1)->getP4();
  }
  else{
    d= p->getDaug(1);
    momv = d->getP4();
    moms = p->getDaug(0)->getP4();
  }
 
 
 
  if (d2type==EvtSpinType::SCALAR) {
    vertex(amp);
  }
  
  if (d2type==EvtSpinType::VECTOR) {
    
    double norm=momv.mass()/(momv.d3mag()*p->mass());
    
    vertex(0,amp*norm*p4_parent*(d->epsParent(0)));
    vertex(1,amp*norm*p4_parent*(d->epsParent(1)));
    vertex(2,amp*norm*p4_parent*(d->epsParent(2)));
  
  }
 
  if (d2type==EvtSpinType::TENSOR) {
 
    double norm=d->mass()*d->mass()/(m_parent*d->getP4().d3mag()*d->getP4().d3mag());
 
   
   vertex(0,amp*norm*d->epsTensorParent(0).cont1(p4_parent)*p4_parent);
   vertex(1,amp*norm*d->epsTensorParent(1).cont1(p4_parent)*p4_parent);
   vertex(2,amp*norm*d->epsTensorParent(2).cont1(p4_parent)*p4_parent);
   vertex(3,amp*norm*d->epsTensorParent(3).cont1(p4_parent)*p4_parent);
   vertex(4,amp*norm*d->epsTensorParent(4).cont1(p4_parent)*p4_parent);
  
  }
 
 
  return ;
}